Providing the sticks of Rhubarb is good and pink turning red then and only then it will be ready to pick.
Have you got forced Rhubarb? Or is it growing naturally?
I know my Rhubarb is only a couple of inches high at the moment so mine wont be ready for at least another 6 weeks or so.

I'm growing it naturally, its only about 15cm at the moment - i'm being a bit previous

And not all varieties of rhubarb go red some stay green!